Uhmm, President Clinton did not pass or sign this law.
As for the pointless semantics of Trump not taking an action that’s stupid and you know it. He chose to change US policy.
Oh I am sorry. Yes, despite passing both houses of Congress in 1995 by overwhelming margins, President Clinton ALLOWED the bill to become law. He didn't actually sign it, but he didn't veto it either (again, massively overwhelming majorities in both chambers). I read both that Clinton had supported Jerusalem as the capital and that the law was passed during his tenure and connected the dots. My bad.
Regardless of that point, US Policy, as written into section 3 of the law is:
(a) STATEMENT OF THE POLICY OF THE UNITED STATES.—
(1) Jerusalem should remain an undivided city in which
the rights of every ethnic and religious group are protected;
(2) Jerusalem should be recognized as the capital of the
State of Israel; and
(3) the United States Embassy in Israel should be established
in Jerusalem no later than May 31, 1999.
So unless the law was amended, that has been the policy since 1995. What President Trump did (or didn't do, depending on how you want to slice that pie) was allow the law to be enacted... and give a speech about it.
Now back to the original question (is President Trump liable). I still say the answer is no. He enacted a law that was put in place over 20 years ago. How people REACT to that is up to them.