If Interpol is too corrupt, countries will start de-funding or ignoring them, denying their agents visas, etc. Their effectiveness would presumably decline quit

If Interpol is too corrupt, countries will start de-funding or ignoring them, denying their agents visas, etc. Their effectiveness would presumably decline quite a bit if a few big/important nations refused to play ball. They can't do much themselves (like actually arrest people) and instead rely on the national counterparts. Additionally, they are audited externally, currently by Norway. Although I'm not entirely sure what would happen if they were to fail an audit.