A 65-year-old woman and a 25-year-old man have been arrested on suspicion of encouraging or assisting a suicide.
Sussex Police confirmed the pair were arrested in the Chichester area and it has been reported that they had planned to accompany a 71-year-old man to Switzerland to end his life.
Police are investigating to see if the man is able to decide to travel himself.
A Sussex Police spokesperson said: “The investigation is looking into what steps, if any, the suspects had made in taking the man out of the country.
“If it is confirmed the man had the mental capacity to make decisions for himself then we would not be able to prevent him travelling.”
More top news
Hurricane Maria is currently pummelling Puerto Rico with 155mph winds after already leaving at least nine people dead in the Caribbean.
Two men have been seriously injured after a gas explosion on an industrial estate.
The two top figures in the far-right group have been charged over leaflets and videos distributed in May.