As part of the complex web of governmental checks and balances, agreements between states often require congressional review and approval. This means that the power to make treaties and agreements does not solely lie with the executive branch but is also subject to congressional oversight.

The Constitution grants Congress the power to regulate commerce between states and with foreign nations. This includes the power to review and approve or reject agreements between states. These agreements can cover a wide range of issues, from economic trade to environmental protection.

One example of an agreement between states that required congressional approval was the Northeast Interstate Dairy Compact. This agreement allowed states in the Northeast to establish minimum prices for milk to ensure that dairy farmers could make a living wage. However, because this agreement could potentially affect interstate commerce, Congress had to approve it before it could be implemented.

Another example is the Interstate Compact on the Placement of Children. This agreement establishes procedures for the adoption of children across state lines. Again, because it involves interstate commerce, Congress had to approve it before it could be put into practice.

Congress has the power to review and reject agreements between states if they are deemed to be unconstitutional or not in the best interest of the country. For example, in 2011, Congress rejected a multistate agreement that would have allowed states to collect sales taxes from online retailers.

It is important to note that not all agreements between states require congressional approval. Some agreements may only require the approval of the states involved. However, if an agreement could potentially affect interstate commerce or national security, it is likely to require congressional approval.

In conclusion, agreements between states are subject to congressional review and approval if they involve interstate commerce or national security. Congress has the power to reject agreements that are deemed to be unconstitutional or not in the best interest of the country. This system of checks and balances ensures that power is not concentrated in any one branch of government and that the interests of all parties are taken into account.