No one should have any faith in government. Faith implies worship, and the state is not to be worshipped.
If you enter into an agreement, you negotiate “in good faith”.
That includes things like eventual collection of the social security money you paid in redeemed at the retirement age set when you entered into the agreement.
Also includes the reasonable expectation that you will be able to draw your retirement money without tax penalty when you reach “age”.
Bill Clinton retroactively raised taxes. That was not good faith. People operated one way and the rules were changed AFTER the fact.
Eaiser to get criminal convictions too if you retroactively create laws and prosecution.