Disregarding for a moment the political and economical repercussions of a Hard Brexit...
What are the immediate legal repercussions of a Hard Brexit, from a stand-point of rights and obligations of legal entities (individuals or otherwise), prior to further modifications of the laws?
My very basic understanding based on 3 years of hearing about it are:
UK laws derived from EU law continue to prevail until modified
Other country's local EU-derived laws will likewise prevail until modified, however, as currently written, those laws will immediately cease to recognize the UK as an EU member
Because of #1 and #2, there are some asymmetries in outcome. For example: Tariffs on imported (EU to UK) goods stay the same, because the local tariffs prevail until modified by new laws (#1); Tariffs on exported (UK to EU) goods immediately increase, because EU countries' local laws immediately recognize the UK as a non-member state (#2).
UK citizens abroad in an EU country may lose the right to be there, and essentially become instant illegal aliens (using a U.S. term), because of #2, unless they obtain a visa like any other non-member citizen
UK non-citizen residents who are EU citizens may continue to reside legally in the UK, because local UK laws derived from EU law continue to prevail until modified (as per #1).
Likewise for corporations ability to do business; in parallel with #4 and #5: Non-UK corporations doing business in the UK will be able to continue to do so, while UK corporations doing business in EU countries would now need comply with "non-member rules," similar to American or Japanese companies. But what specific rights to UK companies enjoy today relative to their American or Japanese competitors when operating in the EU?
The legal status of the Irish border will be what was negotiated in the 1997 Good Friday agreement, which is of an open border, even as individuals become liable for visas and tariffs when crossing (which no one will enforce, but still legally required).
Is this analysis correct, as it relates to the asymmetry of legal outcomes?
What other rights and obligations are directly impactful to any legal entities?