Relevant Bodies Of Law
There are a couple of types of legal standing (i.e. the right right to bring a lawsuit related to something because you are sufficiently connected to the dispute).
An individual has standing to sue concerning the validity of the law if it caused them actual injury or is imminently about to do so if implemented. So, anyone importer who is directly involved in a transaction with a Chinese company subject to the tariff would have standing to sue to declare the tariff ultra vires and invalid because it was beyond the statutory authority of the President to do. The U.S. Department of Justice summarizes the law of individual standing as follows:
The "case or controversy" clause of Article III of the Constitution
imposes a minimal constitutional standing requirement on all litigants
attempting to bring suit in federal court. In order to invoke the
court's jurisdiction, the plaintiff must demonstrate, at an
"irreducible minimum," that: (1) he/she has suffered a distinct and
palpable injury as a result of the putatively illegal conduct of the
defendant; (2) the injury is fairly traceable to the challenged
conduct; and (3) it is likely to be redressed if the requested relief
is granted. See Valley Forge Christian College v. Americans United for
Separation of Church and State, Inc., 454 U.S. 464, 472 (1982);
Gladstone, Realtors v. Village of Bellwood, 441 U.S. 91, 99 (1979);
Simon v. Eastern Kentucky Welfare Rights Organization, 426 U.S. 26, 37
(1976). In addition to the constitutional requirements of Article III,
courts have developed a set of prudential considerations to limit
standing in federal court to prevent a plaintiff "from adjudicating
'abstract questions of wide public significance' which amount to
'generalized grievances' pervasively shared and most appropriately
addressed in the representative branches." See Valley Forge, 454 U.S.
at 474-75, quoting Warth v. Seldin, 422 U.S. 490, 499-500 (1975).
Speculative claims that a proposed governmental action may result in
injury to a plaintiff are insufficient to confer standing. See O'Shea
v. Littleton, 414 U.S. 488, 497 (1974). The required injury must be
both real and immediate, not conjectural or hypothetical. See Golden
v. Zwickler, 394 U.S. 103, 109-10 (1969).
An association can sue on behalf of its members to have a statute or regulation declared to be invalid if an actual injury is suffered by one or more of its members and the injury is pertinent to the purpose of the organization. It can sometimes sue without a direct injury to its members as well if its mission is affected. The American Bar Association has a more precise premier with some case law references here. It explains that (internal block quotation in the original omitted):
Direct Organizational Standing
Organizations have standing to challenge actions that cause them
direct injury. As the Supreme Court recognized in Havens Realty Corp.
v. Coleman, 455 U.S. 363 (1982), direct organizational injury is
typically cognizable in two ways: (A) a diversion of organizational
resources to identify or counteract the allegedly unlawful action, or
(B) frustration of the organization’s mission. While most
jurisdictions require organizations to show only one of these forms of
injury to establish standing, some jurisdictions, notably the Ninth
Circuit, require organizations to show both. Fair Hous. of Marin v.
Combs, 285 F.3d 899, 905 (9th Cir. 2002).
Diversion of resources. An organization may be able to establish
standing by showing that it diverted its resources to identify or
counteract a defendant’s allegedly unlawful actions. To satisfy the
standing requirement, organizations should be prepared to show that
resources that could have otherwise been spent on fulfilling the
organization’s goals were diverted to address the challenged policy or
practice. Fair housing organizations, for example, have frequently
been held to have standing based on their use of testers to identify
allegedly discriminatory housing practices. A circuit split exists,
however, concerning whether diverting resources to support litigation
alone suffices to confer standing—in the D.C., Third, and Fifth
Circuits, litigation expenses alone do not establish standing, while
in the Second, Sixth, Seventh, Eighth, and Eleventh Circuits they can.
Frustration of mission. An organization can also establish standing by
showing a direct injury from conduct or policies that frustrate its
mission. For example, in NYCLU v. N.Y.C. Transit Authority, 684 F.3d
286 (2d Cir. 2011), the Second Circuit held that the NYCLU had
standing to challenge the New York City Transit Authority Board’s
refusal to allow access to its hearings. The denial of access, the
court held, impeded the NYCLU’s ability to observe board hearings and
thereby prepare to represent its clients before the board.
Even in the absence of direct organizational standing, an organization
may be able to establish representational standing based on injuries
to its members. Having a membership is, of course, essential to
establishing representational standing, and it is therefore
particularly useful for organizations such as unions, which frequently
have an interest in seeking redress on behalf of their members. An
organization can establish representative standing by showing that at
least one of its members has standing, that the interests at stake are
germane to the organization’s purpose, and that neither the claim nor
the relief requires participation of the organization’s individual
members. Hunt v. Wash. State Apple Advertising Comm’n, 432 U.S. 333,
Federal regulations such as regulations establishing tariffs pursuant to an alleged statutory authorization must also be adopted in conformity with the
Administrative Procedures Act, which affords standard broader than that which would exist in its absence. As the EPA website explains (links to the statute added by me):
The Administrative Procedure Act (APA) governs the process by which
federal agencies develop and issue regulations. It includes
requirements for publishing notices of proposed and final rulemaking
in the Federal Register, and provides opportunities for the public to
comment on notices of proposed rulemaking. The APA requires most rules
to have a 30-day delayed effective date.
In addition to setting forth rulemaking procedures, the APA addresses
other agency actions such as issuance of policy statements, licenses,
and permits. It also provides standards for judicial review if a
person has been adversely affected or aggrieved by an agency action.
Section 10(a) of the APA states that APA standing to review an agency decision is available in the following circumstances: "Any person suffering legal wrong because of any agency action, or adversely affected or aggrieved by such action within the meaning of any relevant statute, shall be entitled to judicial review thereof."
The basis of the challenge would be under Section 10(e)(3) because the regulation implementing the tariff was allegedly "in excess of statutory jurisdiction, authority, or limitations, or short of statutory right" and possibly also for other reasons.
Application Of Law To Facts
Assuming that the American Chamber of Commerce has members who import goods covered by the tariffs in transactions from China, they would have standing to do so, although better practice would be to including some of those members individually as parties as well. So could any other group with members affected by the tariffs and a pertinent mission statement.
It is less obvious that an individual consumer who is not a party to the transaction upon which the tariff is imposed, or an organization representing such a consumer, would have standing as a result of the indirect injury arising from that consumer paying higher prices for goods subject to the tariff at retail.
Similarly, one cannot generally acquire standing in a case like this one merely because one is a voter or taxpayer with a generalized interest in the United States government acting in accordance with the law.
Subject Matter Jurisdiction And Venue
There are also some technical questions over which federal court has jurisdiction to consider the matter.
Many kinds of civil actions related to federal taxes that are brought before the tax has been paid must be filed in Tax Court (an article I court rather than a part of the judicial branch), but I don't know if that is the case with these tariffs.
There is also an Article III court called the Court of International Trade, in New York City, which is part of the Federal Circuit in the federal courts, that has jurisdiction over many international trade issues arising under federal law. This is probably a court with subject matter jurisdiction over this dispute.
A U.S. District Court would have jurisdiction some in circumstances as well.
The Administrative Procedures Act does not itself specify which court is the proper court.
But, this technical issue is probably in excess of what is necessary to answer the question.