The legal case against the government is interesting.
At the beginning of World War 1, the government shut down parliament, because the country needed action, not talk.
In the 1910s, the government shut down parliament several times and reconvened a new session - as a way to get around the House of Lords, which could be circumvented if the House of Commons approved a bill in three consecutive sessions.
I don't like my own conclusion, but I think the government would have the right to shut down parliament until after Brexit has been achieved. There's a complete lack of clear rules. So BoJo is allowed to play his game...
The legal case against the government is interesting indeed and it seems the verdict will be not a simple YES or NO result, as the justices have been spending enormous time and effort on the remedial aspect of a verdict during the debates, something which is not needed is they'd sit with the government.
Most observers seem to think that they will uphold the government's right to prorogue Parliament and will not rule on the reasons given for that, but will shorten the time of prorogation to the usual length rather than this exceptionally long duration, hence the need for them to be informed on the methods to recall parliament sooner than now planned.
With Parliament sitting and BoJo missing the self-imposed deadlline he thought to be contained in Mrs Merckel's 30 day offer (and which was formalized later by France and Finland yet is now officially rejected by the Brexit Secretary), a vote of no confidence is likely to pass, after which Parliament could -instead of voting for elections as BoJo hopes-, vote for a caretaking PM first, all in order to secure the extension from the EU....