Edit: Of course, illegal activities help to both supplement state funds and hide their source.
We made a sale to the government of a large third world country. They made their first payment and we began to deploy, but obstacles kept arising and nothing more came from it. The subsequent payments weren't made, the product might have disappeared from their warehouse, etc., so we fled the deal.
As it turns out, half the government wanted to end kidnappings, while the other half was perpetrating them. Either side was quick to pocket any lose budget on its way to unwary vendors.
what
If a bunch of goons will say I can't, why can't I hire another bunch of goons that say I can?
While the OP’s point was not well articulated (assuming I’m right about his political leanings), this illustrates the importance of the principle of charity; I.e he’s not mental and/or unredeemable. He just has quirky a worldview
For the record, I disagree with OP on eliminating borders.
Drug trafficking, robberies, kidnapping. Counterfeit products and human trafficking are also two more standard 'revenue streams'. In the case of ISIS apparently it was stealing and selling Oil. Depending on the country you live in, bank robberies either contribute to a gangs' income, or if funds local or international terrorism. This is the main reason police does its best to arrest them. The loss of a bank's £€¥$ is bad, threatening some bank employees and customers is bad, funding the next 'Sri Lanka' is far worse (I am NOT pointing fingers or taking sides - just using this example as it was the most recent).