The proposed “Chequers Agreement” if passed would involve a new treaty committing the UK to ongoing regulatory alignment for goods.
Some Leavers view this with suspicion because they view this kind of alignment as difficult to reverse.
Is this because Treaty law is uniquely difficult to repeal? Or is it more that they do not believe the political will to repeal it would ever be present?
Treaties are very easy to repeal, on a legal and technical level. The difficulties are more symbolic and political. All states have a stake in other states respecting their commitments towards them, more and more so as they enter additional treaties.
But in that case, the treaty itself is secondary. Ongoing regulatory alignment is only good if it grants the UK some economic benefits through a better access to the single market. So the UK would still be in the same position than it is now: Under constant pressure to follow EU rules and precedents, lest it puts the whole agreement into jeopardy.
The EU is going to insist on some enforcement mechanism (there have already been many declarations on that) and it would need to periodically evaluate how much the UK is diverging. The UK increasingly ignoring EU rules would be a major technical and political threat to the single market and would force the EU to push back (although the EU might conceivably be reluctant to be the one officially denouncing the agreement so who knows what would happen…).
Treaties are not difficult to repeal, the issue is the consequences of doing so. Essentially the brexiteers opposing this proposal feel that once in place it will be politically difficult to change.
The main source of inertia is that business will be very resistant to changes, especially if they make the situation worse, e.g. with more paperwork or tariffs or problems with type approvals due to regulatory divergence. The brexiteers view this as an opportunity to make a big change with the political capital built up by the referendum result, which is already dissipating and won't count for much years down the line.
