This is a common misconception. “Reasonable” does have a specific meaning in many legal contexts, and courts typically have a more specific test for what constitutes “reasonable”
For example, a state that has a law which says non-competes much be “reasonable”, may be enforced by the courts as “1 year in duration and within 50 miles”.
The problem is that 50 miles seems reasonable on its face; however, it ignores context.
Let's say you work for a consultancy in a large metropolitan area covering 5MM+ people and this area has 100+ consultancies. There are many groups of these consultancies and they all service different verticals. There are no other major areas with concentrations of business within hundreds of miles (see middle America).
A person may have been working exclusively within the healthcare vertical at one consultancy and would move to another to work in a completely different vertical (e.g., retail). Would 'reasonable' cover this nuance? Probably not, particularly not in the favor of the worker.
Yes, I have lived that exact situation before and I think non-competes should be outlawed entirely. I’m just saying that the word “reasonable” doesn’t make a law open-ended.
It's only subjective until the judiciary establishes a standard test or interpretation. Which they have done in every state that has language like this in their laws.
In practice, you can call up a lawyer in any state that requires non-competes to be "reasonable" and they can tell you more specifically what the court will enforce.