Division of responsibility famously described as an “invitation to struggle” for its control
Trade
The actual negotiation of trade deals has long passed to the President but Congress retains the power to approve them. The trade Act which lets the president fast track trade deals, has not been renewed since Bush.
Congress power to declare war vs the President’s commander in Chief - power to declare war is not often used, Congress’ last formal declaration in 1942
Congressional authorisation gives POTUS a stronger mandate and spreads political responsibility -> Bush Afghanistan 2001 and Iraq 2002
1999 - Kosovo campaign went ahead in the face of explicit refusal by Congress
War Powers Act 1974- POTUS must consult with Congress after the 60 days but if they refuse they have another 30 days to withdraw
Congress power of the purse vs President’s wishes e.g. refusing to back Trump’s wall