Debbie Purdy is concerned her husband could be prosecuted
It is not possible to guarantee a woman with multiple sclerosis her husband would escape prosecution for helping her die, the High Court has heard.
Debbie Purdy, 45, from Bradford, is considering going to a Swiss clinic to end her life, but fears her husband may be charged on his return to the UK.
However, counsel for the Director of Public Prosecutions said assisting a suicide remains illegal.
Ms Purdy will now have to wait for the judges' ruling.
Dinah Rose QC told the hearing: "With respect, Ms Purdy cannot achieve by these proceedings the comfort she says she seeks.
"No one can give her that reassurance that her husband will not be prosecuted because assisting suicide is a criminal offence."
The only way to achieve that. Ms Rose said, would be to persuade parliament to amend the Suicide Act 1961, which makes it an offence to aid, abet, counsel or procure a suicide or a suicide attempt.
Ms Rose rejected accusations that Ms Purdy's right to respect for her private and personal life, enshrined in Article 8 of the European Convention on Human Rights, was being breached because of lack of clarity in the law.
Ms Purdy was diagnosed with primary progressive MS in March 1995. She can no longer walk and is gradually losing strength in her upper body.
She has suggested that at some point she may travel abroad and take a lethal dose of barbiturates prescribed by doctors at a clinic run by Swiss organisation Dignitas.
Ms Purdy wants her husband, Omar Puente, to be at her side when she dies - but fears he may be prosecuted on his return.
Under UK law, helping somebody die carries a sentence of up to 14 years.
The DPP has not prosecuted any relative of the 100 UK citizens who have gone abroad to Dignitas clinics to die.
But the process of how that decision has been reached has not been made clear.
Ms Purdy successfully appealed in June for a judicial review in the High Court on the grounds that the DPP had acted illegally by not providing guidance.
Lord Justice Scott Baker and Mr Justice Aikens reserved judgment on the case.