Only for federal crimes, not state or local level.
A President does not have to execute laws that are unconstitutional.
So he can pardon till the law is repealed
or he can issue executive order to stop enforcement of an unconstitutional law..
You don't have to do it individually. General Pardons for piracy were common during the Golden Age of piracy. Jimmy Carter granted an almost blanket pardon to nearly all Vietnam era draft dodgers. But you can only pardon crimes that have been committed, not future crimes. So you can't in fact "change the law" through pardoning unless you kept on issuing pardons on a daily basis which might rightly earn you an impeachment since it would be a clear violation of the intent of the Constitution.
The pardon power is one of the most important functions of the President from a Constitutional standpoint, and one almost entirely ignored by mainstream Presidents of both parties. Who do you think should be on Rand's list of immediate, week one pardons? My thinking off the top of my head:
1. Edward Snowden
2. Julian Assange
3. Weev
4. Irwin Schiff
First three you'd pardon outright, Irwin Schiff you probably just commute the sentence. Eventually I'd like to see him reduce Bradley Manning's sentence too but probably shouldn't be in the first wave of stuff. Some of the Liberty Reserve guys are starting to get sentenced too. Goes without saying they should get full pardons or immediate commutations as well.
you wouldn't play perpetual pardon games. You'd simply declare the laws on drug prohibition (for example) unconstitutional and order Federal agents not to enforce them.
Whatever gets the job done.