There is no law limiting the ablity for the president to pardon whoever he wants for whatever he wants.
Actually there are, some of which are in the constitution:
https://archive.ph/RebR6
I know your reading comprehension is challenged so I will summarize it:
1. Presidential pardons cannot place the president above the law (doing so would violate the constitution's Take Care clause and Oath clause which bind the president to use his powers to serve the public's interest, not himself)
2. Presidential pardons cannot undermine other parts of the Constitution, including constitutional rights (in 1915 the supreme court ruled that the president cannot force an individual to accept a pardon if it would violate his constitutional rights, in that case the fifth amendment)
3. Presidential pardons cannot violate criminal law (for example - federal law, specifically 18 U.S.C. § 201, prevents public servants, including the president, from exchanging official acts for anything of value for themselves or their family members - 18 U.S. Code § 1510 prohibits corruptly motivated actions, such as promising a pardon to potential witnesses if they refuse to cooperate with an investigation)
4. Presidential pardons cannot license future lawbreaking on the president’s behalf (again, violation of the Take Care and Oath clauses of the constitution)
And as I mentioned before, the president cannot pardon state offenses, as according to article II, section 2, clause 1 of the constitution the president may give clemency only for federal crimes except in cases of impeachment, not state crimes
Believe it or not, the constitution isn't just a buzzword you sycophants like to bring up when it suits you, it's a real existing document that places limits upon government officials, including your "king" who you are currently watching fuck your morbidly obese wife as you type your angry reply with tears in your eyes