prove a check on the administration

Hello,

Could you please explain the part after the comma? I don’t quite understand it.
Last year he [Chief Justice Iftikhar Muhammed Chaudhry] blocked a government bid to sell the majority of the state-owned Pakistan Steel Mills to a private consortium, a blow that proved a rare and embarrassing check on the administration.

Thanks.

proved = proved to be:

...a blow that turned to be a rare and embarrassing check on the administration.

Check on the administration = an act of keeping the administration from doing something.

I see - I just didn't know all the meanings of "check" - an elementary problem (shame on me). I've found in Collins now:
check
18) a break in progress; stoppage
19) a restraint or rebuff
20) a) a person or thing that restrains, halts, etc

Thank you, Ant.

In this case, a check would be a restraint on the powers of the administration.