As with all things run by humans, law is subject to corruption. That is why the better governments in this world have checks and balances on the exercise of power. It prevents authoritarian rulers from acting on a whim, or jailing their critics, etc. That said, there is no perfect system. Law reflects the society that makes them. It is constantly evolving. Slavery was legal for 8,000 years or even longer. In the 21st Century, it is illegal in every country on Earth. While there is still slavery in the world, it is illegal, and when discovered results in arrest. All law is subject to improvement over time.