can you break a regular decision offer?

[ClaremontMom]

There is no law against putting deposits at two schools.

It may not be illegal, but it is unethical and a school may rescind an offer of admission. (Though, admittedly, I have no idea if this happens.)

https://professionals.collegeboard.org/guidance/applications/ethics

(bold emphasis is mine)

Double deposits
Double depositing means putting down a deposit, and thus accepting admission, at more than one college. Since a student can’t attend multiple colleges, it is considered unethical. Why might students and families do this, considering that it would mean forfeiting one deposit? The main reasons are:

To buy time to decide on a college when the student has been accepted by more than one. The usual decision deadline is May 1; by double depositing, a student can delay deciding until fall.
To continue negotiating financial aid offers with more than one college past the May 1 decision deadline.
Because the student is on a waiting list at one college and wants to ensure enrollment somewhere in case of being turned down. This scenario is the only one in which NACAC considers double depositing acceptable.
Why is double depositing unethical?
It’s deceitful. Students know they can only attend one college, so they are essentially lying when they notify more than one that they intend to enroll.

It’s unfair to the college. If the practice continues, colleges may find they can’t predict the size of the incoming class with any accuracy. They may take actions such as enlarging the waiting list or increasing deposit amounts (both of which will impact future applicants).

It’s unfair to other applicants. The double depositor is taking up a spot that could go to another student, who will instead be put on a waiting list or turned down.

What should you do?
Tell students not to submit deposits to more than one college, unless they are wait-listed at their first choice and accepted at another.
Consider instituting a policy of sending each student’s final transcript to only one college.
Warn students that some colleges reserve the right to rescind an offer of admission if they discover that a student has made a double deposit.