Is there a proverb/saying which means "someone in authority can break the rules"?

Solution 1:

One classic riff on the idea you ask about is known as "the Golden Rule—he who has the gold makes the rules."

According to Charles Doyle, Wolfgang Mieder & Fred Shapiro, The [Yale] Dictionary of Modern Proverbs (2012), the earliest print version of this saying appears in Earl Brill, Sex Is Dead (1967), in the following form:

The best I ever heard it stated was in a recent comic strip, "The Wizard of Id." The King was finishing up a speech with the exhortation, "And let us all remember to live by the Golden Rule." Someone asked the Wizard what was the Golden Rule, and he answered: "The one with the gold makes the rule."

Brill doesn't say when Johnny Hart and Brant Parker, writers of The Wizard of Id comic strip released the cartoon in question, but it might have been by 1965, because National League of Postmasters, Postmasters Advocate (1965) has this brief note [snippet view, date not independently confirmed]:

Wonder if it's true? We heard a new definition of the GOLDEN RULE recently. It went like this:

He who has the GOLD, makes the RULE!

Solution 2:

"I guess he is above the law."

(idiomatic) Exempt from the laws that apply to everyone else.

The emperor is above the law.

You may think you're above the law, but you're not.

Solution 3:

How about rank has its privileges, often abbreviated RHIP? It seems to have originated in the military, and the general idea is that the officers can get away with much more than the enlisted soldiers, and the higher your rank, the more you can get away with.

Here's a definition from https://www.waywordradio.org/rhip_1/:

RHIP n.— «The military has produced many acronyms, one of which is RHIP, which stands for, “rank has its privilege.” RHIP is the unofficial way to point out when a person accrues—or assumes—some benefit by virtue of their position.» —“Ownership privileges” by Jim Blasingame Times Daily (Florence, Alabama) May 13, 2007. (source: Double-Tongued Dictionary)

This is further borne out by the rights that higher-ups in the government and in many private industries, such as the film industry, believe that they have because they are important in their field.