In an interview at the White House recently, Donald Trump is quoted threatening a journalist with prison time by saying:
"You can go to prison instead,"
Is the president of the United States legally able to send someone to prison?
In a word: no. The President cannot just order someone to prison.
The Fourth Amendment prohibits unreasonable search and seizure except on probable cause of a crime being committed.
The Fifth Amendment requires felony charges to be brought by a Grand Jury.
The Sixth Amendment requires trial by jury for criminal cases.
It is absolutely correct that a president cannot just point at someone and say, "Jail that person!" and have it happen automatically.
What a president can do is go to the Attorney General and say, "Investigate, indict, and prosecute that person." Then the Justice Department has to attempt those things, subject of course to court and jury approval.
I've heard even private citizens threaten to have someone thrown in jail. In general it just means that the person is going to make a legal complaint that they expect law enforcement will investigate and proceed accordingly.
During the civil war Abraham Lincoln had members of the Maryland state legislature arrested and jailed without charge. He was concerned that Maryland would also secede, leaving D.C. between two Seceded states. To this day the Maryland state song has a verse referring to "resisting the tyrant"- referring to Lincoln!
He was able to do that because article 1 section 9 of the constitution requires "Habeus Corpus" (you must show, to a judge, at least some evidence that the person has committed a crime) "unless when in Cases of Rebellion or Invasion the public Safety may require it."
For example, in the case of the American Civil War, Habeas Corpus was suspended per the Habeas Corpus Suspension Act (1863).
The President is not a Law Enforcement Officer despite his role being ultimately in charge of their policy, so he cannot personally place someone under anything other than citizen's arrest. However, he could possibly order one of the uniformed officers in the Secret Service standing outside the door to arrest the journalist. In this case, the officers could reason that they had probable cause to arrest the journalist under 41 CFR 102-74.420, which carves out photograph permission exceptions where "...security regulations, rules, orders, or directives apply or a Federal court order or rule prohibits it..." (with the rest being mostly permissive to taking photographs for news/non-commercial purposes inside federal facilities), under the theory that the President's forbidding of taking such a photograph counts as a "security order." Under County of Riverside v. McLaughlin, they could then hold the journalist for up to 48 hours in jail before having to release them. It's questionable whether the US Attorney for DC would be willing to follow up on those charges - the President could theoretically pressure her to do so, but it's unlikely the judge would allow further incarceration since the charges are highly unlikely to prevail. With that said, the President would have succeeded in holding the journalist in jail for 48 hours (assuming the journalist's lawyer is not able to get a court order ending the incarceration early).
The officers could then be charged and/or sued for depriving the journalist of their civil rights, arguing that the arrest was unlawful. There would likely be a strong case.
Yes, he can.
As the Commander in Chief of the US armed forces, he would be capable of giving orders to the armed forces - including to members of the law enforcement agencies within those armed forces, such as the Military Police.
Said members of the armed forces would have the right to refuse to obey those orders if they were illegal, but if they weren't, then they would be obligated to do so. For instance, it's possible that rather than ordering the US armed forces to kill Osama Bin Laden, President Obama could have ordered them to arrest him instead, and then transport him to a detention facility like the one in Guantanamo Bay.
This question can be viewed in 2 lights:
1) Can the president legally send you to prison?
2) Can the president physically send you to prison?
The answer to the first is a "qualified" no. He cannot send a US Citizen directly to prison (different rules apply for non-citizens) without the due process of lawful arrest (based upon probable cause of a crime), and a fair trial by a jury of one's peers ... neither of which are options he can bypass in his office as President. THAT BEING SAID, he can direct the Justice Department to dig into your life with a fine-toothed comb, look for every unpaid parking ticket, tax form typo, complaints from ex-lovers 20 years ago... and assuming they find something, he can order them to aggressively prosecute such transgressions. It would almost certainly be tacky in the extreme for him to do so, but... well, he doesn't seem to care about that.
The answer to the second is a scary yes... through ultimately illegal or unethical means, declaring you an enemy of the state, declaring martial law, etc. The men in black pick you up and nobody hears from you again. This is why it's super critical that people in positions of power show and practice a deference to the spirit of the law.
Not just no... hell no.
The founding fathers were so worked up against bills of attainders, in fact, that they explicitly banned them in the US constitution (I §§ 9.3 and 10.1) in both Federal Law and State Law:
The United States Constitution forbids legislative bills of attainder: in federal law under Article I, Section 9, and in state law under Article I, Section 10. The fact that they were banned even under state law reflects the importance that the framers attached to this issue.
In 1996 John Yoo wrote an influential article in the California Law Review in which he laid out an expansive theory of presidential primacy. According to the abstract of an article critical of Yoo's opinion it
became the legal basis for [...] the claim that neither constitutional protections nor other provisions of domestic and international law constrain treatment of suspected terrorists.
Detaining a photographer would require that the s/he was considered a terrorist or a comparable risk to national security. But as I remarked in a comment, this may happen faster than one thinks, especially in times of perceived national emergencies: Think of labeling investigative journalists traitors and risks to national security.
While Yoo's is currently not a main stream opinion it exerted considerable influence in the decisions of the Bush Jr. administration. Obviously, whether something is legal or not is ultimately decided in court; that such an opinion can be upheld by a legal scholar leaves the possibility open that a court of the future could find a detention legal which we would find illegal today.
A sitting president can have someone sent to jail or prison. One only need look at the Obama/D’Souza case. Dinesh D’Souza is a conservative author and filmmaker who made a movie critical of Obama’s life and presidency.He was prosecuted to the fullest extent by Eric Holder. President Trump pardoned D’Souza.