Levonelle is available over-the-counter
If the campaign is successful it could place a question mark over the legality of all forms of contraception, except natural and barrier methods.
Popularly dubbed the morning-after pill, the drug levonelle can actually be taken up to 72 hours after intercourse.
The 1861 Offences Against the Person Act prohibits the supply of any "poison or other noxious thing" with intent to cause miscarriage.
SPUC's argument is based on the fact that the drug stops an embryo from implanting in the lining of the womb.
Judicial review
The organisation successfully applied last year for leave to bring a judicial review of the government's decision to reclassify the drug as suitable for over-the-counter sale.
The court will be asked to consider what is the precise moment at which a woman becomes pregnant.
Is it when the egg is fertilised, or when the resulting embryo is implanted in the womb?
If it is the former, then the court could rule that emergency contraception causes a miscarriage and is illegal.
Family planning campaigners warn that, in theory, such a decision could affect the legality of everyday birth control which operates in the same way.
Richard Gordon QC, appearing for SPUC, told the court: "We say that fertilisation, when sperm meets egg, is the start of pregnancy.
"If that is right, it follows a miscarriage can occur any time thereafter.
"Neither choice, nor consequences can justify the destruction of a human life once it has started at fertilisation."
'Unsupervised abortion'
Women over the age of 16 have been able to buy the drug from pharmacists since the beginning of last year without needing to see a doctor first. Previously it was only available on prescription from a doctor.
More than a third of all emergency contraception is now dispensed in this way.
SPUC's national director John Smeaton told BBC Radio 4's Today programme the presentation of the morning after pill as so called emergency contraception was a "cynical deception of women".
"We think it is deliberately promoted as contraception because... if you talk directly about abortion women do not like it," he said.
"What we have is almost entirely unsupervised abortion by pill."
Opposition
She said a ruling in favour of the legal challenge would be disastrous.
"In a civilised modern society the government would have to step in to take measures to allow women to benefit from modern science of contraception," she told Today.
Shelley Mehigan, of the Royal College of Nursing Sexual Health Forum said: "If this outrageous action succeeds it will be a retrograde step in the history of contraception in this country.
"This could effect millions of women by preventing them from accessing hormonal contraception to take responsibility for preventing unwanted pregnancies."
Previous attempt
An attempt has already been made in the House of Lords to prevent the medication being sold over-the-counter.
Conservative peer Lady Young had argued that pharmacists were too busy to offer enough medical advice to women buying the pill. However, this attempt was defeated by peers.
Levonelle comprises two tablets of 750 micrograms of the a form of the hormone progestogen.
It prevents unwanted pregnancy in several ways, depending on what stage of her menstrual cycle a woman is in when she has unprotected sex: