I was curious to know how could a congressman block a business deal from going trhough. example , like one company buying out another.

What would be the political action he could do. like bring it up to some department or board or something to decide.


basicaly my question relates to me trying to write a stage play, and in this stage play, this man, lets call him Mr.A has just finalised a deal, buying a a major airline company, but he already owns one of the biggest, so he's treatening to corner the market. So a congressman intervenes, does some sort of political action that blocks the deal, doesnt kill it , but blocks it, puts the breaks on it.

so what would that political action be? what are his options.

thanks guys