There are several checks.
Firstly, any user with more than 3,000 reputation can cast a reopen vote. When 5 people have voted the question is reopened.
Secondly, moderators review each other and they can reverse the decision with a single vote. If there is a particular question you have in mind flag it for moderator attention to speed this along.
Thirdly, you can post a question here on meta raising the issue. This will help with the first two points as well as more people will see the question.
Finally, you can send an e-mail to the team - use the "contact us" link at the foot of every page. Though this should be reserved for the most serious problems.