Why wouldn't they be allowed to do it?
You have the choice of not viewing the website.
You have the choice of not viewing the website.
But the EU posted a press release last year that they are investigating this, as it could breach the DMA. [1]
The Guardian doesn't fall under the DMA though.
[1] https://ec.europa.eu/commission/presscorner/detail/en/ip_24_...