There’s a bug difference between telling people who are hopelessly hooked on something that they can’t have it any more, and telling someone they’ll never be allowed to start on it to begin with.

Also, this law doesn’t have to completely eliminate smoking to have done it’s job. All they’re trying to do is reduce it, which reducing availability certainly will

Also, the answer to your actual question is no. There’s definitely no way to block people from using any particular characters at the kernel level.

What you seem to be asking for is a way to absolutely forbid all software from writing certain characters to files, and/or from reading those characters. Aside from requiring that the kernel inspect all data in detail before letting other software have it, which would slow everything way down, it would prevent anyone from reading or writing binary data which happens to contain those sequences of bytes by coincidence. Binary data includes things like the programs which make the system work, so blocking those characters would be terminal

It ought to look like a bunch of □, which is the glyph generally used to indicate that the font has nothing to represent the character.

Specifically you’d expect U+25A1 □ WHITE SQUARE