Why did isolationists want these laws?

Answer 1

What laws are you specifically referring to? Isolationism is usually brought up, in the United States, as a discussion of politics during WWII where there was a fierce debate on whether or not the US should involve itself in the war or not. Although that is technically an interventionism vs non-interventionism debate, where isolationists tend to side with non-interventionists.

Isolationism is typically in reference to a country's foreign policy. Where an isolationist country will oppose any interaction with other countries. This means not getting involved in international politics or trade.

If this question is in reference to any law involving those areas... Isolationists support Protectionist trading policy which means that they do not import or export their goods to other countries. Depending on economic theories this can help or hurt a country. This is essentially a statement that if its not made here we won't sell it here. In places where industry cannot compete with foreign industry this can be applied. Although it can hurt because your industry will no longer have access to foreign markets. Free trade laws are against protectionism as the flow of goods into a country from other countries can be limited by tariffs (a tax placed on goods coming into a country).

Isolationists also generally support laws with non-interventionism, where hope to keep peace by not involving themselves in foreign politics. This keeps them from joining alliances or going to war in any circumstance beyond defending against a direct invasion of their territory (self-defense).

These are ongoing debates.