ID is a realization (based in part on mathematical reasoning) that neo-Darwinian model of evolution is inadequate model for explaining the observed phenomena of life and its evolution. That is certainly a much healthier attitude toward science than pretending to know what is not known and silencing the doubters using censorship, courts and police.
A designer would have to be supernatural (i.e. not subject to the laws of physics) or natural and subject to those laws.
That's a straw-man. ID doesn't postulate anything about lawfulness of the "designer". It simply says that the observed complexity of life requires far greater level of intelligence and foresight, or far more powerful algorithm than the algorithm of "random mutation" and "natural selection" of the neo-Darwinian dogma. The nature of that additional intelligence/algorithm is an open question that needs to be scientifically investigated.
As to the "laws of physics" as presently understood, that, too need not be held as the final word on the subject. Many among the greatest physicists of 20th century, including Planck, Einstein, Dirac, Schrodinger, de Broglie,... had realized that our present modeling foundation in physics, the quantum fields, are merely an approximate (linearized) computational algorithm for some unknown underlying reality.
If the designer is natural in origin, then it would have to have been designed by another designer –again supernatural or natural.
Not correct. It is perfectly conceivable within ID that some more fundamental physical laws provide mechanisms sufficient to explain composition of computationally more powerful systems from the less powerful ones. Cellular automata, such as Conway's Game of Life, demonstrate that such schemes are at least mathematically possible. Steven Wolfram as well as the scientists associated with the Santa Fe Institute on Complex Systems believe that the vastly greater intelligence responsible for origin of life and evolution may be of this perfectly lawful kind (albeit with laws still largely unknown).
In a similar later case, Kitzmiller vs. The Dover Area School District involving ...
When a "scientific theory" starts using courts and the brute force of State to silence doubters, it's a sure sign that its days are numbered and that its defenders know it.
And that's why ID isn't science. ID is simply criticism of evolution theory based on the hypothesis that complex things require a designer. They then look for complex things and repeat the hypothesis. No evidence that supports the "complex things need a designer" is ever offered. The hypothesis just gets restated in different ways. If a real scientist were to suggest that a designer existed and that his existance explained the origin of life in the universe, then he would have to prove that a designer could exist and explain a mechanism for his coming into being and suggest an experiment to support his hypothesis. If found, he would have a theory.