Which laws in which Northern controlled Congress are you referring to?
There were several. The one causing the lion's share of trouble for the South was the "Navigation act of 1817." It gave Northern shipping industries a virtual monopoly on the carrying of Southern cargo.
There was also the "Warehousing Act" and several others who's names I have forgotten.
Subsidies paid to Northern industries (such as fishing subsidies) also hurt the South to the benefit of the North. Mail carrying contracts were given to Northern shipping companies which made them more profitable than shipping companies that did not get such contracts.
Expenditures on railroads, canals, and harbors greatly favored the North
You may be surprised to hear this, but virtually *ALL* of the South's trade with Europe was controlled by New York companies. They also controlled the packet shipping industry that took goods from port to port.