Surely you understand the difference between a cop declining to issue a speeding ticket and a federal "discretionary" policy that makes it de facto legal to violate standing immigration law at scale.
There is no difference. People often complain during the pandemic that the San Francisco police department has seemingly instituted a "discretionary" policy that makes it de facto legal to violate traffic law at scale, you know, including speeding, not stopping at stop signs, not yielding to pedestrians. https://www.reddit.com/r/sanfrancisco/comments/11nbnxw/san_f...
Maybe you are misunderstanding. A single cop deciding "okay today I'm letting you off with a warning" is quite different from the President directing the entire Federal bureaucracy to not enforce existing immigration law. If for some reason a large jurisdiction, say maybe the state of California, decided that it was policy to let everyone off with a warning for speeding infractions, then, if I squint hard enough and ignore a wide range of second and third order effects, then yeah maybe they are similar.